Remote plasma source

ABSTRACT

The present invention provides a remote plasma source mountable on a process chamber and connectable on one end to a gas inletting system and on the other end to a gas distribution system disposed in a process chamber. Preferably, a conventional microwave generator is utilized to deliver microwaves into a remote chamber to excite a gas passed therethrough into an excited state.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus, including asystem and individual system components, for concurrent processing ofmultiple wafers in the fabrication of integrated circuits. Moreparticularly, the present invention provides a staged vacuum systemhaving one or more process chambers which share one or more utilities,one or more loadlock chambers and a transfer chamber connected to boththe loadlock chambers and the process chambers.

BACKGROUND OF THE RELATED ART

The term "cluster tool" generally refers to a modular, multichamber,integrated processing system having a central wafer handling module anda number of peripheral process chambers. Cluster tools have becomegenerally accepted as effective and efficient equipment formanufacturing advanced microelectronic devices. Wafers are introducedinto a cluster tool where they undergo a series of process stepssequentially in various process chambers to form integrated circuits.The transfer of the wafers between the process chambers is typicallymanaged by a wafer handling module located in a central transfer region.Typically, cluster tools are of two different types: single waferprocessing or batch wafer processing. Single wafer processing generallyrefers to a chamber configuration in which a single wafer is located forprocessing. Batch wafer processing generally refers to a chamberconfiguration in which multiple wafers are positioned on a turntable andare processed at various positions within the chamber as the turntablerotates through 360°. A cluster tool configured for batch processingallows multiple wafers, typically from four (4) to seven (7) wafers, tobe simultaneously processed in a single chamber.

FIGS. 1 and 2 show examples of commercially available batch processingsystems 10. FIG. 1 is a top schematic view of a radial cluster tool forbatch processing that is available from Novellus Corporation. Thiscluster tool includes two batch processing chambers 12, 13 that eachhold six wafers 14 for processing. A single wafer handling robot 16located in a transfer chamber 18 is used to transfer wafers from aloadlock chamber 20 to a first batch processing chamber 12 one by one,where the wafers are sequentially received on a turntable 22 beforereceiving the same processing steps. The wafers may then be transferred,one by one, to a second batch processing chamber 13, where the wafersundergo additional processing steps. Typically, wafers are loaded intothe system one at a time and moved into a chamber where they receivepartial processing at various positions as the wafers are rotated 360°on the turntable.

FIGS. 2A and 2B are top and side schematic views of a cluster tool 10for batch processing that is available from Mattson Technology. Theloadlock chamber 20 and transfer chamber 18 have a common wafer elevator19 that allow the wafers to be staged within the transfer chamber. Atransfer robot 16 transports wafers to the processing chamber, such as achemical vapor deposition (CVD) chamber, which holds up to four wafers.The wafers are then returned to the wafer elevator and eventuallywithdrawn from the tool.

One disadvantage of batch processing, including the processing performedin the cluster tools described above, is that batch processingfrequently provides poor deposition uniformity from the center of thewafer to the edge of the wafer. Process uniformity is important in orderto obtain uniformity of deposition on the wafer. The poor uniformity ofbatch processing systems is a direct result of having multiple wafersbeing partially processed at multiple stations within a single chamber.

An alternative approach to improve process uniformity is the use ofsingle wafer processing chambers. Single wafer processing is generallyconsidered to provide a higher degree of control over processuniformity, because a single wafer is positioned in a process chamberwhere it undergoes a complete process step, such as a deposition step oran etch step, without having to be moved to a different position.Furthermore, the components of a single wafer processing chamber can bepositioned concentrically or otherwise relative to the single wafer.

FIG. 3 shows a top schematic view of a cluster tool 10 having multiplesingle wafer processing chambers 12 mounted thereon. A cluster toolsimilar to that shown in FIG. 3 is available from Applied Materials,Inc. of Santa Clara, Calif. The tool includes a loadlock chamber 20 anda transfer chamber 18 having a wafer handling module 16 for moving thewafers from location to location within the system, in particular,between the multiple single wafer processing chambers 12. Thisparticular tool is shown to accommodate up to four (4) single waferprocessing chambers 12 positioned radially about the transfer chamber.

There is a need for a vacuum processing system that provides bothuniform wafer processing and high throughput. More particularly, thereis a need for an integrated system and process chambers that work incooperation to incorporate single wafer architecture with batch waferhandling techniques. It would be desirable to have a system with a smallfootprint/faceprint and which requires lower capital investments andoperating costs than typical cluster tools.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for exciting oneor more cleaning gases into a plasma state and delivering the excitedgases into a process chamber. In one embodiment of the invention, aremote plasma source utilizing a conventional microwave generator isprovided to deliver energy into a compact remote chamber housing anenergy transparent applicator tube. The resulting excited gas speciesare delivered into a process chamber.

In another aspect of the invention, the remote plasma source is mounteddirectly on the chamber so that gases can be delivered through a gasinletting system through the remote source alp and then into thechamber. The remote assembly is disposed horizontally on the processchamber and connected on one end to the inletting system and on theother end to a gas distribution system in a process chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention are described inconjunction with the following drawing figures, in which:

FIG. 1 is a top schematic view of a radial cluster tool for batchprocessing that is available from Novellus Corporation;

FIGS. 2A and 2B are top and side schematic views of a linear clustertool for batch processing that is available from Mattson Technology;

FIG. 3 is a top schematic view of a cluster tool having a plurality ofsingle wafer processing chambers;

FIG. 4 is a perspective view of one embodiment of the vacuum processingsystem of the present invention;

FIG. 5 is a top schematic view of one embodiment of the vacuumprocessing system of the present invention;

FIG. 6 is a front end view of one embodiment of the vacuum processingsystem of the present invention;

FIG. 7 is a back end view of one embodiment of the vacuum processingsystem of the present invention;

FIG. 8 is a perspective view of the front end loading system of thepresent invention;

FIG. 9 is a substantially front perspective view of the inside of aloadlock chamber of the present invention;

FIG. 10 is a cross sectional view of a loadlock chamber of the presentinvention;

FIG. 11 is a perspective view of a loadlock chamber showing a gate valveand actuating assembly mounted on the front of the loadlock chamber;

FIG. 12 is a perspective view of another embodiment of a loadlockchamber of the present invention;

FIG. 13 is a top view of the present invention showing a transferchamber having a transfer wafer handling member located therein and afront end platform having two wafer cassettes and a front end waferhandling member mounted thereon for wafer mapping and centering;

FIG. 14 is a cross sectional side view of a transfer chamber of thepresent invention;

FIG. 15 is a top view of a transfer chamber and a processing chambershowing a wafer handling member of the present invention mounted in thetransfer chamber and in a retracted position ready for rotation withinthe transfer chamber or extension into another chamber;

FIG. 16 is a top view of a transfer chamber and a processing chambershowing a wafer handling member of the present invention mounted in thetransfer chamber and in an extended position wherein the blades arepositioned in the processing chamber;

FIG. 17 is a cross sectional view of a magnetically coupled actuatingassembly of a wafer handling system of the present invention;

FIG. 18 is a perspective view of one embodiment of a processing chamberof the present invention;

FIG. 19 is a cross sectional view of one embodiment of a processingchamber of the present invention;

FIG. 20 is an exploded view of the gas distribution assembly;

FIG. 21 is a top view of a processing chamber of the present inventionwith the lid removed;

FIG. 22a is a schematic diagram of a vacuum system of the presentinvention;

FIG. 22b is a schematic diagram of another vacuum system of the presentinvention;

FIG. 23 is a perspective view of a remote plasma chamber mounted on aprocessing chamber;

FIG. 24 is a cross sectional view of a remote plasma chamber mounted ona processing chamber; and

FIG. 25 is an illustrative block diagram of the hierarchical controlstructure of a computer program for process control;

FIG. 26 is a top view of a transfer chamber showing a time optimal pathfor a robot of the present invention;

FIG. 27 is a graph showing the optimal velocity profile for the pathshown in FIG. 26;

FIG. 28 is a top view of a transfer chamber showing a time optimal pathfor a robot of the present invention; and

FIG. 29 is a graph showing the optimal velocity profile for the pathshown in FIG. 28.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides a cassette-to-cassette vacuumprocessing system which concurrently processes multiple wafers andcombines the advantages of single wafer process chambers and multiplewafer handling for high quality wafer processing, high wafer throughputand reduced system footprint. In accordance with one aspect of theinvention, the system is preferably a staged vacuum system whichgenerally includes a loadlock chamber for introducing wafers into thesystem and which also provides wafer cooling following processing, atransfer chamber for housing a wafer handler, and one or more processingchambers each having two or more processing regions which are isolatablefrom each other and preferably share a common gas supply and a commonexhaust pump. Isolatable means that the processing regions have aconfined plasma zone separate from the adjacent region which isselectively communicable with the adjacent region via an exhaust system.The processing regions within each chamber also preferably includeseparate gas distribution assemblies and RF power sources to provide auniform plasma density over a wafer surface in each processing region.The processing chambers are configured to allow multiple, isolatedprocesses to be performed concurrently in at least two regions so thatat least two wafers can be processed simultaneously in separateprocessing regions with a high degree of process control provided byshared gas sources, shared exhaust systems, separate gas distributionassemblies, separate RF power sources, and separate temperature controlsystems. For ease of description, the terms processing regions andchamber may be used to designate the zone in which plasma processing iscarried out.

FIGS. 4-7 illustrate the processing system 100 of the present inventionschematically. The system 100 is a self-contained system having thenecessary processing utilities supported on a main frame structure 101which can be easily installed and which provides a quick start up foroperation. The system 100 generally includes four different regions,namely, a front end staging area 102 where wafer cassettes 109 (shown inFIG. 8) are supported and wafers are loaded into and unloaded from aloadlock chamber 112, a transfer chamber 104 housing a wafer handler, aseries of tandem process chambers 106 mounted on the transfer chamber104 and a back end 108 which houses the support utilities needed foroperation of the system 100, such as a gas panel 103, power distributionpanel 105 and power generators 107. The system can be adapted toaccommodate various processes and supporting chamber hardware such asCVD, PVD and etch. The embodiment described below will be directed to asystem employing a DCVD process, such as a silane process, to depositsilicon oxide. However, it is to be understood that these otherprocesses are contemplated by the present invention.

Front End Staging Area

FIG. 8 shows the front end staging area 102 of the system 100 whichincludes a staging platform 110 having one or more wafer cassetteturntables 111 rotationally mounted through the platform 110 to supportone or more wafer cassettes 109 for processing. Wafers housed in thewafer cassettes 109 are loaded into the system 100 through one or moredoors 137 disposed through a front cover 139 (both shown in FIG. 6). Afront end wafer handler 113, such as a robot, is mounted on the stagingplatform 110 adjacent to the wafer cassette turntables 111 and theloadlock chamber door 209 (shown in FIG. 11). Preferably, the front endwafer handler 113 includes a wafer mapping system to index the wafers ineach wafer cassette 109 in preparation for loading the wafers into aloadlock cassette disposed in the loadlock chamber 112. One waferhandler used to advantage in the present system which includes a wafermapping system is available from Equippe Technologies, Sunnyvale,Calif., as model nos. ATM 107 or 105. The wafer mapping sensor verifiesthe number of wafers and orientation of the wafers in the cassette 109before positioning the wafers in the loadlock chamber 112 forprocessing. An exhaust system such as ULPA filter, available fromEnviroco Corporation located in Alburquerque, N. Mex.; Flanders locatedin San Rafael, Calif., or Filtra located in Santa Ana, Calif., ismounted to the bottom of a support shelf 115 above the platform 110 toprovide particle control on the front end of the system. A computermonitor 117 is supported on a monitor shelf 119 above the support shelf115 to provide touch control to an operator.

Loadlock Chamber

FIG. 9 shows a substantially side perspective view of one embodiment ofa loadlock chamber 112 of the present invention. The loadlock chamber112 includes a sidewall 202, a bottom 204 and a lid 206. The sidewall202 defines a loadlock loading port 208 for loading wafers into andunloading wafers out of the vacuum system 100. Passages 210 and 212 aredisposed in the sidewall 202 opposite the loading port 208 to allowwafers to be moved from the loadlock chamber 112 into the transferchamber 104 (not shown). Slit valves and slit valve actuators are usedto seal the passages 210 and 212 when isolation or staged vacuum isdesired. A service port 214 and service door or window 216 are disposedon one end of the loadlock chamber 112 to provide service and visualaccess to the loadlock chamber 112.

A loadlock cassette 218 is disposed within the loadlock chamber 112 tosupport the wafers in a spaced relationship in the loadlock chamber 112so that a wafer handler can pass between the wafers to place and removewafers from the loadlock cassette 218. The loadlock cassette 218preferably supports two or more wafers in a side-by-side arrangement onwafer seats 220. The wafer seats 220 are formed on cassette plates 222which are supported in spaced relation on a movable shaft 224.Preferably, the plates 222 are made of anodized aluminum and can handleup to about 14 wafers spaced vertically apart by about 0.6 inch. In theembodiment shown in FIG. 9, six rows of wafer seats 220 are provided tosupport a total of twelve (12) wafers.

Each wafer seat 220 defines at least two grooves 226 in which a supportrail 228 is disposed to support a wafer above the wafer seat 220 toprovide a cooling gas passage below the wafer. In a preferredembodiment, at least two rails 228 made of a ceramic are provided tosupport the wafer, but more rails may be used. Wafers are supportedabout 1 to about 15 mils above the wafer seats 220 on the ceramic rails228 to provide uniform cooling of the wafers.

The shaft 224 is disposed through the bottom 204 of the loadlock chamber112 and supports the cassette plates 222 within the loadlock chamber112. A motor, such as a stepper motor or other elevator system, isdisposed below the bottom 204 of the loadlock chamber 112 and moves theshaft 224 upwardly and downwardly within the loadlock chamber 112 tolocate a pair of wafers in alignment with a wafer handler for loading orunloading wafers from the loadlock chamber 112.

FIG. 10 shows a side view of the loadlock chamber 112 with the frontremoved. The cassette plates 222 include a central portion 230 throughwhich the shaft 224 extends to support the plates 222. The outer edgesof the cassette plates 222 are supported in a spaced relationship byspacers 232 which are secured thereto with pins 234. Each plate 222defines a central channel 236 formed into each plate to form a slot forthe robot blade to pass under the wafer when the wafer is supported onthe seat 220.

FIG. 11 shows a front perspective view of the loadlock chamber 112.Loading door 209 and door actuator 238 are shown in a closed and sealedposition. The loading door 209 is connected to the actuator 238 onmovable shafts 240. To open the door 209, the actuator 238 tilts awayfrom the side wall 202 to unseal the door 209 and then the shafts 240are lowered to provide clearance of the door 209 and access to the port208 (shown in FIG. 9). One door actuator used to advantage with thepresent invention is available from VAT, located in Switzerland.

An on-board vacuum pump 121 is mounted on the frame 101 adjacent theloadlock chamber 112 and the transfer chamber 104 to pump down theloadlock chamber and the transfer chamber. An exhaust port 280 isdisposed through the bottom of the loadlock chamber 112 and is connectedto the pump 121 via exhaust line 704. The pump is preferably a highvacuum turbo pump capable of providing milliTorr pressures with very lowvibration. One vacuum used to advantage is available from Edward HighVacuum.

The transfer chamber 104 is preferably pumped down through the loadlockchamber 112 by opening a pair of slit valves sealing passages 210, 212and pumping gases out through the exhaust port 280 located in theloadlock chamber 112. Gas-bound particles are kept from being swept intothe transfer chamber 104 by continually exhausting gases out of thesystem through the loadlock chamber 112. In addition, a gas diffuser 231is disposed in the loadlock chamber to facilitate venting up toatmosphere. The gas diffuser 231 is preferably a conduit disposed in theloadlock chamber and connected to a gas purge line such as an N₂ purgegas line. The gas diffuser 231 distributes the purge gas along a largersurface area through a plurality of ports 233 disposed along the lengthof the diffuser, thereby decreasing the time needed to vent the chamberup to atmosphere. The vacuum system of the present invention will bedescribed in more detail below.

Dual Position Loadlock Chamber

FIG. 12 shows a cut-away perspective view of another embodiment of aloadlock chamber 112 of the present invention. The loadlock chamber 112includes chamber walls 202, a bottom 204, and a lid 206. The chamber 112includes two separate environments or compartments 242, 244 and atransfer region 246. Compartments 242, 244 include a wafer cassette ineach compartment 242, 244 to support the wafers therein. Eachcompartment 242, 244 includes a support platform 248 and a top platform250 to define the bottom and top of the compartments 242, 244. A supportwall 252 may be disposed vertically within the compartments 242, 244 tosupport platforms 248, 250 in a spaced relationship. Transfer region 246includes one or more passages 192 for providing access from the loadlockchamber 112 into the transfer chamber 104 (not shown). Passages 192 arepreferably opened and closed using slit valves and slit valve actuators.

Compartments 242, 244 are each connected to an elevator shaft 224, eachof which is connected to a motor, such as a stepper motor or the like,to move the compartments upwardly or downwardly within the loadlockchamber 112. A sealing flange 256 is disposed peripherally within theloadlock chamber 112 to provide a sealing surface for support platform248 of compartment 242. Sealing flange 258 is similarly disposed toprovide a sealing surface for support platform 250 of compartment 244.The compartments 242, 244 are isolated from one another by sealingflanges 256, 258 to provide independent staged vacuum of thecompartments 242, 244 within the loadlock chamber 112.

A back side pressure is maintained in spaces 260, 262 through a vacuumport disposed therein. A vacuum pump is connected to the spaces 260, 262via exhaust lines 264 so that a high vacuum can be provided in thespaces 260, 262 to assist in sealing the platforms 248, 250 against thesealing flanges 256, 258.

In operation, compartments 242, 244 can be loaded or unloaded in theposition shown in FIG. 12. Loading doors 209 and actuators 238, such asthose described above (shown in FIG. 11), are provided through the frontwall (not shown) at the upper and lower limits of the loadlock chamber112 corresponding with compartments 242, 244. The pressure in a selectedcompartment is pumped down after wafers have been loaded into thecompartment via exhaust lines 287, 289 and the selected compartment ismoved into the transfer region 246. Compartments 242, 244 moveindependently into the transfer region 246 by the stepper motor. Theadvantage of having upper and lower compartments 242, 244 is thatprocessing of one set of wafers can occur while a second set of wafersis loaded into the other compartment and that compartment is pumped downto the appropriate pressure so that the compartment can be moved intothe transfer region 246 and in communication with the transfer chamber104.

Wafer Center-Finding

FIG. 8 shows the wafer handling robot 113 on the front end 102 of thesystem 100 which includes a wafer transfer blade for transferring wafersfrom the wafer cassettes 109 into and out of the loadlock chamber 112.The wafers do not always lie in precisely the same position within eachwafer cassette 109 and, therefore, are not positioned identically on theblade when they are transferred into the loadlock cassette 218. Thus,before the wafer is loaded into the loadlock cassette, the preciselocation of the wafer on the robot blade must be determined and providedto a controlling computer. Knowing the exact center of the wafer allowsthe computer to adjust for the variable position of each wafer on theblade and deposit the wafer precisely in the desired position in aloadlock cassette 218 so that, ultimately, the wafer handler in thetransfer chamber can precisely position the wafers in the processchambers 106.

An optical sensing system 170 which provides wafer position data(preferably the center coordinate of the wafer) to enable the robot toprecisely position the wafers in the loadlock cassette 218 is providedadjacent to each cassette turntable 111 on the front end 102. Eachsystem comprises three optical sensors 172 mounted on the lower support173 of a C clamp 174 adjacent the cassette turntable 111 along a lineperpendicular to the path of the robot blade and three optical emitters176 positioned on the upper support 177 of the C clamp 174 aligned withthe associated sensors so that the sensors intercept the light beamsfrom the associated emitters. Typically, each pair comprises aconventional infrared emitter and sensor.

The output of the sensors is converted by associated analog-to-digitalconverters into digital signals which are applied as input to the systemcomputer for use in computing the center coordinate of the wafers asthey enter the loadlock chamber 112, and controlling the operation ofthe robot drive motors as required to enable precise positioning of eachwafer in the loadlock cassette 218 by the robot 113. Details of thesensing and motor control circuitry are described in more detail in U.S.Pat. No. 4,819,167, by Cheng et al., which is incorporated herein byreference.

Transfer Chamber

FIG. 13 shows a top view of the processing system 100 of the presentinvention. The transfer chamber body includes sidewalls 302 and bottom304 and is preferably machined or otherwise fabricated from one piece ofmaterial, such as aluminum. A lid (not shown) is supported on thesidewalls 302 during operation to form a vacuum enclosure. The sidewall302 of transfer chamber 104 supports processing chambers 106 andloadlock chamber 112. The sidewall 302 defines at least two passages 310on each side through which access to the other chambers on the system isprovided. Each of the processing chambers 106 and loadlock chamber 112include one or more slit valve openings and slit valves which enablecommunication between the processing chambers, the loadlock chamber andthe transfer chamber while also providing vacuum isolation of theenvironments within each of these chambers to enable a staged vacuumwithin the system. The bottom 304 of the transfer chamber 104 defines acentral passage 306 in which a wafer handler 500, such as a robotassembly, extends and is mounted to the bottom of the transfer chamber.In addition, the bottom 304 defines a plurality of passages 308 throughwhich one or more slit valve actuators extend and are sealably mounted.A gas purge port 309 is disposed through the bottom 304 of the transferchamber 104 to provide a purge gas during pump down.

FIG. 14 shows the transfer chamber 104 in partial cross-section. Thepassages 310 disposed through the sidewalls 302 can be opened and closedusing two individual slit valves or a tandem slit valve assembly. Thepassages 310 mate with the wafer passages 610 in process regions 618,620 (shown in FIG. 15) to allow entry of wafers 502 into the processingregions 618, 620 in chambers 106 for positioning on the wafer heaterpedestal 628.

Slit valves and methods of controlling slit valves are disclosed byTepman et al. in U.S. Pat. No. 5,226,632 and by Lorimer in U.S. Pat. No.5,363,872, both of which are incorporated herein by reference.

Transfer Chamber Wafer Handler

FIG. 15 shows a top schematic view of a magnetically coupled robot 500of the present invention in a retracted position for rotating freelywithin the transfer chamber 104. A robot having dual wafer handlingblades 520, 522 is located within the transfer chamber 104 to transferthe wafers 502 from one chamber to another. A "very high productivity"(VHP) type robot which can be modified and used to advantage in thepresent invention is the subject of U.S. Pat. No. 5,469,035 issued onNov. 21, 1995, entitled "Two-axis Magnetically Coupled Robot", and isincorporated herein by reference. The magnetically coupled robot 500comprises a frog-leg type assembly connected between two vacuum sidehubs (also referred to as magnetic clamps) and dual wafer blades 520,522 to provide both radial and rotational movement of the robot bladeswithin a fixed plane. Radial and rotational movements can be coordinatedor combined in order to pickup, transfer and deliver two wafers from onelocation within the system 100 to another, such as from one processingchamber 106 to another chamber.

The robot includes a first strut 504 rigidly attached to a first magnetclamp 524 at point 525 and a second strut 506 rigidly attached to asecond magnet clamp 526 (disposed concentrically below the first magnetclamp 524) at point 527 (See also FIG. 17). A third strut 508 isattached by a pivot 510 to strut 504 and by a pivot 512 to the waferblade assembly 540. A fourth strut 514 is attached by a pivot 516 tostrut 506 and by a pivot 518 to the wafer blade assembly 540. Thestructure of struts 504, 508, 506, 514 and pivots 510, 512, 516, 518form a "frog leg" type connection between the wafer blade assembly 540and the magnet clamps 524, 526.

When magnet clamps 524, 526 rotate in the same direction with the sameangular velocity, then robot 500 also rotates about axis A in this samedirection with the same velocity. When magnet clamps 524, 526 rotate inopposite directions with the same absolute angular velocity, then thereis no rotation of assembly 500, but instead, there is linear radialmovement of wafer blade assembly 540 to a position illustrated in FIG.16.

Two wafers 502 are shown loaded on the wafer blade assembly 540 toillustrate that the individual wafer blades 520, 522 can be extendedthrough individual wafer passages 310 in sidewall 302 of the transferchamber 104 to transfer the wafers 502 into or out of the processingregions 618, 620 of the chambers 106. The magnetically coupled robot 500is controlled by the relative rotational motion of the magnet clamps524, 526 corresponding to the relative speed of two motors. A firstoperational mode is provided in which both motors cause the magnetclamps 524, 526 to rotate in the same direction at the same speed.Because this mode causes no relative motion of the magnet clamps, therobot will merely rotate about a central axis A, typically from aposition suitable for wafer exchange with one pair of processing regions618, 620 to a position suitable for wafer exchange with another pair ofprocessing regions. Furthermore, as the fully retracted robot is rotatedabout the central axis A, the outermost radial points 548 along the edgeof the wafer define a minimum circular region 550 required to rotate therobot. The magnetically coupled robot also provides a second mode inwhich both motors cause the magnet clamps 524, 526 to rotate in oppositedirections at the same speed. This second mode is used to extend thewafer blades 520, 522 of the wafer blade assembly 540 through thepassages 310 and into the processing regions 618, 620 or, conversely, towithdraw the blades therefrom. Other combinations of motor rotation canbe used to provide simultaneous extension or retraction of the waferblade assembly 540 as the robot 500 is being rotated about axis A.

To keep the wafer blades 520, 522 of the wafer blade assembly 540directed radially away from the rotational axis A, an interlockingmechanism is used between the pivots or cams 512, 518 to assure an equaland opposite angular rotation of each pivot. The interlocking mechanismmay take on many designs, including intermeshed gears or straps pulledaround the pivots in a figure-8 pattern or the equivalent. One preferredinterlocking mechanism is a pair of metal straps 542 and 544 that arecoupled to and extend between the pivots 512, 518 of the wafer bladeassembly 540. The straps 542, 544 cooperate to form a figure-8 aroundthe pivots 512, 518. However, it is preferred that the straps 542, 544be individually adjustable and positioned one above the other. Forexample, a first end of the first strap 542 may pass around the backside of pivot 512 and be fixedly coupled thereto, while a second endpasses around the front side of pivot 518 and is adjustably coupledthereto. Similarly, a first end of the second strap 544 may pass aroundthe back side of pivot 518 and be fixedly coupled thereto, while asecond end passes around the front side of pivot 512 and is adjustablycoupled thereto. The adjustable couplings between the straps and thefront sides of the pivots 512, 518 are preferably provided with a springthat pulls a precise tension on the strap. Once the tension isestablished, the end of the strap is firmly held in position with ascrew or other fastener. In FIGS. 15 and 16, the straps are also shownpassing around a rod 546 at the base of the U-shaped dual blade.

FIG. 16 shows the robot arms and blade assembly of FIG. 15 in anextended position. This extension is accomplished by the simultaneousand equal rotation of magnet clamp 526 in a clock-wise direction andmagnet clamp 524 in a counter-clockwise rotation. The individual blades520, 522 of the wafer blade assembly 540 are sufficiently long to extendthrough the passages 310 and center the wafers 502 over the pedestals628 (See FIG. 19). Once the wafers 502 have been lifted from the bladesby a pair of lift pin assemblies, then the blades are retracted and thepassages 310 are closed by a slit valve and actuator as described above.

FIG. 17 shows a cross sectional view of a robot drive system mounted tothe central opening 306 in the bottom 304 of the transfer chamber 104.The magnetic coupling assembly is configured to rotate magneticretaining rings 524, 526 about the central axis A, thereby providing adrive mechanism to actuate the wafer blade assembly 540 within thesystem, both rotationally and linearly. Additionally, the magneticcoupling assembly provides rotational movement of the magnetic retainingrings 524, 526 with minimal contacting moving parts within the transferchamber 104 to minimize particle generation. In this embodiment, therobot features are provided by fixing first and second stepper or servomotors in a housing located above or below the transfer chamber 104,preferably below, and coupling the output of the motors to magnetic ringassemblies located inwardly of and adjacent to a thin wall 560. The thinwall 560 is connected to the upper or lower wall 304 of the transferchamber 104 at a sealed connection to seal the interior of the transferchamber from the environment outside of the chamber. Magnetic retainingrings 524, 526 are located on the vacuum side of transfer chamber 104,adjacent to and surrounding the thin wall 560.

A first motor output 562 drives a first shaft 572 and intermeshed gears580 to provide rotation to the first magnetic ring assembly 582 that ismagnetically coupled to the first magnetic retaining ring 524. A secondmotor output 564 drives a second shaft 586 and intermeshed gears 590 toprovide rotation to the second magnetic ring assembly 592 (a concentriccylindrical member disposed about assembly 582) that is magneticallycoupled to a second magnetic retaining ring 526. Rotation of each motorprovides rotational outputs 562, 564 that rotate the magnet ringassemblies 582, 592 which magnetically couple the rotary output throughthe thin wall 560 to magnetic retaining rings 524, 526, thereby rotatingthe struts 504, 506, respectively, and imparting rotational andtranslational motion to the wafer blade assembly 540.

To couple each magnet ring assembly to its respective magnetic retainingring, each magnet ring assembly 582, 592 and magnetic retaining ring524, 526 preferably include an equal plurality of magnets paired withone another through wall 560. To increase magnetic couplingeffectiveness, the magnets may be positioned with their poles alignedvertically, with pole pieces extending therefrom and toward the adjacentmagnet to which it is coupled. The magnets which are coupled areflipped, magnetically, so that north pole to south pole coupling occursat each pair of pole pieces located on either side of the thin walledsection. While magnetic coupling is preferred, direct coupling of themotors to the retaining rings may also be employed.

Optimal Path Trajectory of Robot

The movement of the robot 500 while transferring wafers is primarilyconstrained by reliance on friction between the wafer and the dual waferblades 520, 522 for gripping the wafers. Both linear and rotationalmovement of each wafer blade 520, 522 must be controlled to avoidmisalignment of the wafers. Movement of the robot is preferablyoptimized to provide a minimum wafer transfer time to improveproductivity while avoiding wafer misalignment.

Optimization of robotic movement has been described in publications,such as Z. Shiller and S. Dubowsky, "Time Optimal Path Planning forRobotic Manipulators with Obstacles, Actuator, Gripper and PayloadConstraints", International Journal of Robotics Research, pp. 3-18,1989, and Z. Shiller and H. H. Lu, "Comparison of Time-Optimal MotionsAlong Specified Paths", ASME Journal of Dynamic Systems, Measurementsand Control, 1991, which provide mathematical approaches to finding thetime optimal path between two or more points for a given robotconfiguration. The approach generally involves a mathematicalapproximation of a specified path and calculation of an optimal velocityprofile, and the calculation of an optimal path by varying pathparameters to find the minimum time required for the robot to follow aspecified path within all known constraints.

A mathematical solution to optimization of robot movement typicallyinvolves the solution of multiple algebraic equations and non-lineardifferential equations or non-linear matrix differential equations, andis preferably assisted by a computer. However, persons skilled in theoptimization methods can often identify the more optimum path withoutresolving the matrices or the equations.

Optimization of wafer movement using the robot 500 described aboveresulted in definition of several time optimal paths which are expectedto significantly improve productivity of the processing system of thepresent invention. The time optimal paths are shown in FIGS. 26-29. FIG.26 shows the optimal paths 1500, 1502, 1504 for moving wafers betweenchambers positioned 180° apart on the processing platform and FIG. 27shows the optimal velocity profile for a path 1500 halfway between paths1502, 1504 taken by wafers on the dual wafer blades 520, 522. FIG. 28shows the optimal paths 1510, 1512, 1514 for moving wafers betweenchambers positioned 90° apart on the processing platform and FIG. 29shows the optimal velocity profile for a path 1510 halfway between paths1512, 1514 taken by wafers on the dual wafer blades 520, 522.

FIGS. 27 and 29 also show the maximum velocities which can be attainedby the robot 500 along the paths 1500, 1510 when wafers are notpositioned on the dual wafer blades 520, 522. The robot 500 ispreferably controlled so that the dual wafer blades 520, 522 follow theoptimal paths using the optimal velocity profiles shown in FIGS. 26-29when moving wafers through the transfer chamber 104.

Process Chambers

FIG. 18 shows a perspective view of one embodiment of a tandemprocessing chamber 106 of the present invention. Chamber body 602 ismounted or otherwise connected to the transfer chamber 104 and includestwo processing regions in which individual wafers are concurrentlyprocessed. The chamber body 602 supports a lid 604 which is hindgedlyattached to the chamber body 602 and includes one or more gasdistribution systems 608 disposed therethrough for delivering reactantand cleaning gases into multiple processing regions.

FIG. 19 shows a schematic cross-sectional view of the chamber 106defining two processing regions 618, 620. Chamber body 602 includessidewall 612, interior wall 614 and bottom wall 616 which define the twoprocessing regions 618, 620. The bottom wall 616 in each processingregion 618, 620 defines at least two passages 622, 624 through which astem 626 of a pedestal heater 628 and a rod 630 of a wafer lift pinassembly are disposed, respectively. A pedestal lift assembly and thewafer lift will be described in detail below.

The sidewall 612 and the interior wall 614 define two cylindricalannular processing regions 618, 620. A circumferential pumping channel625 is formed in the chamber walls defining the cylindrical processingregions 618, 620 for exhausting gases from the processing regions 618,620 and controlling the pressure within each region 618, 620. A chamberliner or insert 627, preferably made of ceramic or the like, is disposedin each processing region 618, 620 to define the lateral boundary ofeach processing region and to protect the chamber walls 612, 614 fromthe corrosive processing environment and to maintain an electricallyisolated plasma environment between the electrodes. The liner 627 issupported in the chamber on a ledge 629 formed in the walls 612, 614 ofeach processing region 618, 620. The liner includes a plurality ofexhaust ports 631, or circumferential slots, disposed therethrough andin communication with the pumping channel 625 formed in the chamberwalls. Preferably, there are about twenty four ports 631 disposedthrough each liner 627 which are spaced apart by about 15° and locatedabout the periphery of the processing regions 618, 620. While twentyfour ports are preferred, any number can be employed to achieve thedesired pumping rate and uniformity. In addition to the number of ports,the height of the ports relative to the face plate of the gasdistribution system is controlled to provide an optimal gas flow patternover the wafer during processing.

FIG. 21 shows a cross sectional view of the chamber illustrating theexhaust system of the present invention. The pumping channels 625 ofeach processing region 618, 620 are preferably connected to a commonexhaust pump via a common exhaust channel 619. The exhaust channel 619is connected to the pumping channel 625 of each region 618, 620 byexhaust conduits 621. The exhaust channel 619 is connected to an exhaustpump via an exhaust line (not shown). Each region is preferably pumpeddown to a selected pressure by the pump and the connected exhaust systemallows equalization of the pressure within each region.

Referring back to FIG. 19, each of the processing regions 618, 620 alsopreferably include a gas distribution assembly 608 disposed through thechamber lid 604 to deliver gases into the processing regions 618, 620,preferably from the same gas source. The gas distribution system 608 ofeach processing region includes a gas inlet passage 640 which deliversgas into a shower head assembly 642. The shower head assembly 642 iscomprised of an annular base plate 648 having a blocker plate 644disposed intermediate a face plate 646. An RF feedthrough provides abias potential to the showerhead assembly to facilitate generation of aplasma between the face plate 646 of the showerhead assembly and theheater pedestal 628. A cooling channel 652 is formed in a base plate 648of each gas distribution system 608 to cool the plate during operation.An inlet 655 delivers a coolant fluid, such as water or the like, intothe channels 652 which are connected to each other by coolant line 657.The cooling fluid exits the channel through a coolant outlet 659.Alternatively, the cooling fluid is circulated through the manifold.

The chamber body 602 defines a plurality of vertical gas passages foreach reactant gas and cleaning gas suitable for the selected process tobe delivered in the chamber through the gas distribution system. Gasinlet connections 641 are disposed at the bottom of the chamber 106 toconnect the gas passages formed in the chamber wall to the gas inletlines 639. An o-ring is provided around each gas passage formed throughthe chamber wall on the upper surface of the chamber wall to providesealing connection with the lid as shown in FIG. 21. The lid includesmatching passages to deliver the gas from the lower portion of thechamber wall into a gas inlet manifold 670 positioned on top of thechamber 1 as shown in FIG. 20. The reactant gases are delivered througha voltage gradient feed-through 672 and into a gas outlet manifold 674which is connected to a gas distribution assembly.

The gas input manifold 670 channels process gases from the chamber gasfeedthroughs into the constant voltage gradient gas feedthroughs, whichare grounded. Gas feed tubes (not shown) deliver or route the processgases through the voltage gradient gas feedthroughs 672 and into theoutlet manifold 674. Resistive sleeves surround the gas feed tubes tocause a linear voltage drop across the feedthrough preventing a plasmain the chamber from moving up the gas feed tubes. The gas feed tubes arepreferably made of quartz and the sleeves are preferably made of acomposite ceramic. The gas feed tubes are disposed within an isolatingblock which contains coolant channels to control temperature and preventheat radiation and also to prevent liquefaction of process gases.Preferably, the insulating block is made of Delrin. The quartz feedtubes deliver gas into a gas output manifold 674 which channels theprocess gases to the blocker plate 644 and into the gas distributionplate 646.

The gas input manifold 670 (see FIG. 20) also defines a passage whichdelivers cleaning gases from a chamber gas feedthrough into the remoteplasma source. These gases bypass the voltage gradient feedthroughs andare fed into a remote plasma source where the gases are activated intovarious excited species. The excited species are then delivered to thegas distribution plate at a point just below the blocker plate through aconduit disposed in gas inlet passage 640. The remote plasma source anddelivery of reactant cleaning gases will be described in detail below.

The gas lines 639 which provide gas into the gas distribution systems ofeach processing region are preferably connected to a single gas sourceline and are therefore shared or commonly controlled for delivery of gasto each processing region 618, 620. The gas line(s) feeding the processgases to the multi-zone chamber are split to feed the multiple processregions by a t-type coupling. To facilitate flow into the individuallines feeding each process region, a filter, such as a sintered nickelfilter available from PALL or Millipore, is disposed in the gas lineupstream from the splitter. The filter enhances the even distributionand flow of gases into the separate gas feed lines.

The gas distribution system comprises a base plate having a blockerplate disposed adjacent to its lower surface. A face plate is disposedbelow the blocker plate to deliver the gases into the processingregions. In one embodiment, the base plate defines a gas passagetherethrough to deliver process gases to a region just above the blockerplate. The blocker plate disperses the process gases over its uppersurface and delivers the gases above the face plate. The holes in theblocker plate can be sized and positioned to enhance mixing of theprocess gases and distribution over the face plate. The gases deliveredto the face plate are then delivered into the processing regions in auniform manner over a wafer positioned for processing.

A gas feed tube is positioned in the gas passage and is connected at oneend to an output line from a remote plasma source. One end of the gasfeed tube extends through the gas outlet manifold to deliver gases fromthe remote plasma source. The other end of the gas feed tube is disposedthrough the blocker plate to deliver gases beyond the blocker plate tothe region just above the face plate. The face plate disperses the gasesdelivered through the gas feed tube and then delivers the gases into theprocessing regions.

While this is a preferred gas distribution system, the gases from theremote plasma source can be introduced into the processing regionsthrough a port provided through the chamber wall. In addition, processgases could be delivered through any gas distribution system which ispresently available, such as the gas distribution system available fromApplied Materials, Inc. of Santa Clara, Calif.

Heater Pedestal

FIG. 19 shows a heater pedestal 628 which is movably disposed in eachprocessing region 618, 620 by a stem 626 which is connected to theunderside of a support plate and extends through the bottom of thechamber body 602 where it is connected to a drive system 603. The stem626 is preferably a circular, tubular, aluminum member, having an upperend disposed in supporting contact with the underside of the heaterpedestal 628 and a lower end closed off with a cover plate. The lowerend of the stem is received in a cup shaped sleeve, which forms theconnection of the stem to the drive system. The stem 626 mechanicallypositions the heater pedestal 628 within the processing region and alsoforms an ambient passageway through which a plurality of heater plateconnections can extend. Each heater pedestal 628 may include heatingelements to heat a wafer positioned thereon to a desired processtemperature. The heating elements may include for example a resistiveheating element. Alternatively, the heater pedestal may be heated by anoutside heating element such as a lamp. A pedestal used to advantage inthe present invention is available from Applied Materials, Inc., ofSanta Clara, Calif. The pedestal may also support an electrostaticchuck, a vacuum chuck or other chucking device to secure a wafer thereonduring processing.

The drive system includes linear electric actuators made by IndustrialDevice Corporation located in Novabo, Calif. The heater assembly israised and lowered by moving the transfer housing up or down to aprocess, clean, lift and release position. The transfer housing isconnected to the actuator on one side and a linear slide on the otherthrough a carriage plate. The connection between the actuator and thecarriage is made via a flexible (ball and socket) joint to allow for anymisalignment. The linear slide and carriage plate are biased against oneanother to prevent rotation and bending thereof. A bellows surrounds thestem of the heater and connects to the chamber bottom on one end and tothe transfer housing on the other end. A seal ring is provided in agroove in the stem to seal the outer surface of the lower end of thestem in the sleeve. Leveling of the heater with respect to the faceplateis achieved with the use of three screws.

Alternatively, the drive system 603 includes a motor and reductiongearing assembly suspended below the chamber 106 and connected to adrive belt to a conformable coupling and lead screw assembly. A transferhousing is received on the lead screw assembly, which is guided up anddown and held against rotation by a linear slide. The heater liftmechanism is held against the chamber with the drive collar. The heaterassembly is raised and lowered by a lead screw which is driven by astepper motor. The stepper motor is mounted to the heater lift assemblyby a motor bracket. The stepper motor drives the lead screw in abellows. The bellows turn the lead screw to raise or lower the heaterassembly to the process, lift and release positions. A seal ring isprovided in a groove in the stem to seal the outer surface of the lowerend of the stem in the sleeve.

Wafer Positioning Assembly

The stem 626 moves upwardly and downwardly in the chamber to move theheater pedestal 628 to position a wafer thereon or remove a wafertherefrom for processing. A wafer positioning assembly includes aplurality of support pins 651 which move vertically with respect to theheater pedestal 628 and are received in bores 653 disposed verticallythrough the pedestal. Each pin 651 includes a cylindrical shaft 659terminating in a lower spherical portion 661 and an upper truncatedconical head 663 formed as an outward extension of the shaft. The bores653 in the heater pedestal 628 include an upper, countersunk portionsized to receive the conical head 663 therein such that when the pin 651is fully received into the heater pedestal 628, the head does not extendabove the surface of the heater pedestal.

The lift pins 651 move partially in conjunction with, and partiallyindependent of, the heater pedestal 628 as the pedestal moves within theprocessing region. The lift pins can extend above the pedestal 628 toallow the robot blade to remove the wafer from the processing region,but must also sink into the pedestal to locate the wafer on the uppersurface of the pedestal for processing. To move the pins 651, the waferpositioning assembly includes an annular pin support 655 which isconfigured to engage lower spherical portions 661 of the lift pins 651and a drive member which positions the pin support 655 to selectivelyengage the lift pins 651 depending on the position of the heaterpedestal 628 within the processing region. The pin support 655,preferably made from ceramic, extends around the stem 626 below theheater pedestal 628 to selectively engage the lower spherical portionsof the support pins.

A drive assembly lifts and lowers the shaft 630 and connected pinsupport 655 to move the pins 651 upwardly and downwardly in eachprocessing region 618, 620. The pin drive member is preferably locatedon the bottom of the chamber 106 to control the movement of the pinsupport platform 655 with respect to the pedestal heater 628.

Vacuum System and Chamber Pumps

The vacuum control system for the processing system 100 of the presentinvention may include a plurality of vacuum pumps in communication withvarious regions of the system, with each region having its own setpointpressure. However, the transfer of wafers from one chamber or region toanother chamber or region requires the opening of slit valves whichallow the environments of the communicating regions to mix somewhat andthe pressures to equilibrate.

FIG. 22a shows a schematic diagram of the vacuum system 700 of thepresent invention. The loadlock chamber 112 and the transfer chamber 104preferably share a vacuum pump 121 mounted on the main frame 101 of thesystem adjacent the loadlock chamber and the transfer chamber. Theloadlock chamber 112 is pumped down from atmosphere by pump 121 throughexhaust port 280 disposed through the body of the loadlock chamber. Thevacuum pressure in the transfer chamber 104, as indicated by pressuregauge 705, is provided by communication with the loadlock chamber 112 sothat the pressure in the transfer chamber is always equal to or greaterthan the pressure in the loadlock chamber and any particles present inthe loadlock chamber will not be drawn into the transfer chamber 104.Exhaust port 280 in loadlock chamber 112 is connected to pump 121 viaexhaust line 704. A pressure gauge 706 is positioned along exhaust line704 upstream from an isolation valve 708 to monitor the pressure in theloadlock chamber at any given time. Isolation valve 708 is located inexhaust line 704 between the pressure gauge 706 and the pump 121 toregulate the pressure in the loadlock chamber. A vacuum switch 710 isalso provided in communication with the exhaust line between theisolation valve 708 and the pump 121. The pump 121 is preferably aroughing pump, but depending on the application may be any type of pumpsuch as a turbomolecular pump, a cryogenic pump or the like. Gas ventlines 712, 714 are connected to the loadlock chamber 112 and thetransfer chamber 104, respectively, to provide a vent gas, such asnitrogen, into these chambers.

Process chambers 106 are connected to a pump 720, such as a roughingpump, cryogenic pump or turbomolecular pump, via exhaust port 619 andexhaust line 722. A throttle valve 724, or the like, is located in theexhaust line to regulate the pressure in the processing regions 618, 620of chambers 106 during operation. A valve controller 726, preferably apart of the system controller, provides a control signal to the throttlevalve 724 based upon the pressure indicated by the vacuum gauge 728.Preferably, an exhaust port 619 is in communication with each processingregion (shown in FIG. 21) and an exhaust line from each processingregion tees into a single exhaust line 722 which is connected to thepump 720.

According to one aspect of the present invention, the slit valves incommunication with the transfer chamber 104 and the vacuum controllersof each chamber 106 and the loadlock chamber 112 are operated in amanner that reduces the amount of contaminants entering the transferchamber from either the loadlock chamber or any of the chambers 106. Theinvention requires the pressure in the loadlock chamber to be greaterthan or equal to, preferably greater than, the pressure in an adjacentchamber or region prior to opening the slit valve that will providecommunication therebetween. The loadlock pressure should only be greaterthan atmospheric when open to the front end. The pressure should belower than the transfer chamber pressure when opening to transfer invacuum. It is particularly important that the transfer chamber 104 be ata high relative pressure when placed in communication with a processchamber, because the contaminant levels can be particularly great. Forexample, where the setpoint pressure in a processing chamber 106 isabout 10⁻³ torr, the pressure in the transfer chamber should be greaterthan or equal to 10⁻³ torr, most preferably greater than about 10⁻²torr, before opening the slit valves to transfer wafers into or out ofthe chamber 106.

The pressure in the transfer chamber is controlled in two ways. First,the vacuum in the transfer chamber is established by opening the slitvalve(s) between the loadlock chamber 112 and the transfer chamber 104and then pulling a vacuum in the loadlock chamber 112. In this manner,the pressure in the transfer chamber should never be lower than thepressure in the loadlock chamber and the only gas flow therebetweenshould be from the transfer chamber to the loadlock chamber 112. It isanticipated that so long as the transfer chamber is not in communicationwith any processing chambers, the slit valves between the transferchamber and the loadlock chamber may remain open. Second, the transferchamber is provided with a purge gas inlet, such as from an argon ornitrogen source. The purge gas may be delivered to the transfer chambercontinuously or only as needed to provide a sufficient high pressure tocause a positive gas flow out of the transfer chamber.

In a particularly preferred mode, the slit valves to the loadlockchamber 112 should always be closed during wafer transfer between thetransfer chamber 104 and a processing chamber 106, in order to avoid thepossibility of drawing the pressure in the transfer chamber down belowthe pressure in the processing chamber. This condition could result in amultitude of contaminants from the processing chamber entering thetransfer chamber and even the loadlock, thereby exposing an entirecassette of wafers.

FIG. 22b shows a schematic diagram of two pumping systems used toadvantage with the dual chamber loadlock described above. As can be seenfrom the figure, the two compartments can be pumped down together orselectively pumped down to a desired vacuum.

Gas Box and Supply

Outside of the chamber on the back end of the system, there is a gassupply panel containing the gases that are to be used during depositionand cleaning. The particular gases that are used depend upon thematerials to be deposited onto the wafer or removed from the chamber.The process gases flow through an inlet port into the gas manifold andthen into the chamber through a shower head type gas distributionassembly. An electronically operated valve and flow control mechanismcontrol the flow of gases from the gas supply into the chamber.

In one embodiment of the invention the precursor gases are deliveredfrom the gas box to the chamber where the gas line tees into twoseparate gas lines which feed gases through the chamber body asdescribed above. Depending on the process, any number of gases can bedelivered in this manner and can be mixed either before they aredelivered to the bottom of the chamber or once they have entered the gasdistribution plate.

Power Supplies

An advanced compact RF ("CRF") power delivery system is used for eachprocessing region 618, 620 with one system connected to each gasdistribution system. A 13.56 MHz RF generator, Genisis Series,manufactured by ENI, is mounted on the back end of the system for eachchamber. This high frequency generator is designed for use with a fixedmatch and regulates the power delivered to the load, eliminating theconcern about forward and reflected power. Up to 1250 watts may besupplied into load impedances with a VSWR of less than or equal to 1:5.To interface a high frequency RF generator and a low frequency RFgenerator to a process chamber, a low pass filter is designed into thefixed match enclosure.

A 350 kHz RF generator manufactured by ENI, is located in an RFgenerator rack on the back end of the system and linked to the fixed RFmatch by coaxial cable. The low frequency RF generator provides both lowfrequency generation and fixed match elements in one compact enclosure.The low frequency RF generator regulates the power delivered to the loadreducing the concern about forward and reflected power.

Remote Clean Module

FIGS. 23 and 24 show a perspective and cross sectional view of a remoteclean module 800 of the present invention. In accordance with theinvention, the remote clean module 800 is connected to the processingregions 618, 620 of chamber 106 through the inlet port 820. The remoteclean module 800 supplies gas that is used to remove deposited materialfrom the interior surfaces of the chamber after a sequence of processruns.

The remote clean module 800 includes a source of a precursor gas 804, aremote activation chamber 806 which is located outside of the processingchamber 106, a power source 808 for activating the precursor gas withinthe remote activation chamber, an electronically operated valve and flowcontrol mechanism 810, and a conduit or pipe 812 connecting the remotechamber to the processing chamber via a conduit 811. The valve and flowcontrol mechanism 810 delivers gas from the source of precursor gas 804into the remote activation chamber 806 at a user-selected flow rate. Theactivation chamber 806 includes an aluminum enclosure 803 having a gasfeed tube 813 disposed therethrough. The power source 808 generatesmicrowaves which are guided by a wave guide 805 into the enclosure 803.The tube 813 is transparent to microwaves so that the microwavespenetrate the tube and activate the precursor gas to form a reactivespecies which is then flowed through the conduit 812 into the gasdistribution assembly and then into a processing chamber. In otherwords, the upper electrode or shower head 608 is used to deliver thereactive gas into the processing regions of the chamber. In thedescribed embodiment, the remote chamber is a ceramic tube and the powersource is a 2.54 GHz microwave generator with its output aimed at theceramic tube.

Optionally, there may also be a source of a minor carrier gas 814 thatis connected to the remote activation chamber through another valve andflow control mechanism 816. The minor carrier gas aids in the transportof the activated species to the deposition chamber. The gas can be anyappropriate nonreactive gas that is compatible with the particularcleaning process with which it is being used. For example, the minorcarrier gas may be argon, nitrogen, helium, hydrogen, or oxygen, etc. Inaddition to aiding in the transport of activated species to thedeposition chamber, the carrier gas may also assist in the cleaningprocess or help initiate and/or stabilize the plasma in the depositionchamber.

In the described embodiment, there is a filter 818 in the conduit orpipe through which the activated species passes before entering thedeposition chamber. The filter removes particulate matter that mighthave been formed during the activation of the reactive species. In thedescribed embodiment, the filter is made of ceramic material having apore size of about 0.01 to about 0.03 microns. Of course, othermaterials can also be used, for example, Teflon.

It should be noted that the filter can also be used to remove unwantedmaterials that might have been produced as byproducts of the reactionwithin the remote chamber. For example, if the reactive gas is CF₄ orSF₆, or some other halogen compound containing either carbon or sulfur,an activated carbon or sulfur species will be present as a byproduct ofthe activation process. It is generally desired, however, that carbonand sulfur not be present in the deposition chamber. This is why thesecompounds are generally not used in conventional dry cleaning processeswhere the activation occurs entirely within the deposition chamber.However, when the activation is performed remotely, as described herein,these materials can be easily removed by using an appropriate filtermaterial. Such filter materials are readily available in the commercialmarket and are well-known to persons of ordinary skill in the art.

In the described embodiment, the precursor is NF₃. The flow rate ofactivated species is about 0.5 liters to about 2 liters per minute andthe chamber pressure is about 0.5 to about 2.5 Torr. To activate theprecursor gas, the microwave source delivers about 500 to about 1500Watts to the activation chamber. Within the deposition chamber, the RFsources supply about 100 to about 200 Watts to the plasma. For thepresent system, this implies a voltage between the upper and lowerelectrodes of about 15 to about 20 volts. The precise voltage andcurrent are pressure dependent, i.e., the current is proportional to thepressure given a fixed voltage. In any event, it is only necessary toinduce a gentle plasma within the chamber, which only need be strongenough to sustain the activated species that has been flown into thechamber from the remote source.

By using NF₃ as the feed gas, chambers that have been deposited withsilicon (Si), doped silicon, silicon nitride (Si₃ N+₄) and silicon oxide(SiO₂) can be cleaned. The cleaning rate for deposited film is about 2microns/minute for silicon nitride and about 1 micron/minute forsilicon, doped silicon, and silicon oxide. These cleaning rates are twoto four times faster than the conventional cleaning process whichemploys only a local plasma with a power level of about 1 to about 2kilowatts at 13.56 MHz RF.

Though a microwave generator is used in the described embodiment toactivate the precursor gas, any power source that is capable ofactivating the precursor gas can be used. For example, both the remoteand local plasmas can employ DC, radio frequency (RF), and microwave(MW) based discharge techniques. In addition, if an RF power source isused, it can be either capacitively or inductively coupled to the insideof the chamber. The activation can also be performed by a thermallybased, gas break-down technique, a high intensity light source, or anx-ray source, to name just a few.

In general, the reactive gases may be selected from a wide range ofoptions, including the commonly used halogens and halogen compounds. Forexample, the reactive gas may be chlorine, fluorine or compoundsthereof, e.g. NF₃, CF₄, SF₆, C₂ F₆, CCl₄, C₂ Cl₆. Of course, theparticular gas that is used depends on the deposited material which isbeing removed. For example, in a tungsten deposition system, a fluorinecompound gas is typically used to etch and/or remove the depositedtungsten.

Because of the use of a local plasma in conjunction with the remoteplasma, the remote activation chamber can be placed farther away fromthe chamber. Thus, only tubing is needed to connect the two remotesources to the local source. Some quenching of the activated species(i.e., deactivation of the activated species) may occur during thetransfer. However, the local source compensates for any such quenchingthat may occur. In fact, some long lived activated species (e.g. F*)typically do not return to the ground state when quenched, but ratherthey transition to an intermediate state. Thus, the amount of energythat is required to reactivate the quenched species is much less than isrequired to activate the gas in the remote activation chamber.Consequently, the local activation source (e.g. plasma) need not be ahigh energy source.

It should also be noted that by placing the remote source at a distancefrom the deposition chamber, the short lived radicals that are producedduring the activation process will be quenched more completely than thelong lived radicals as both are transferred to the deposition chamber.Thus, the reactive gas that flows into the deposition chamber willcontain primarily the long lived radicals that have survived thetransfer. For example, if NF₃ is the reactive gas, two radicals areproduced in the remote activation chamber, namely, N* and F*. Thenitrogen radical is short lived and the fluorine radical is long lived.The nitrogen radical will typically not survive a long transfer from theremote chamber to the deposition chamber, whereas a large percentage ofthe fluorine radicals will survive. This is a form of natural filteringthat occurs in the system that may be very desirable. In the case ofnitrogen radicals, for example, it is sometimes preferable that they notbe present in the deposition chamber because their presence may resultin the formation of N_(x) H_(y) F_(z) compounds, which can harm thepump. When the activation is performed in the deposition chamber,however, as in the case of conventional cleaning techniques, there is noeasy way to eliminate the nitrogen radicals that are produced.

In the dry cleaning process, chamber pressure can be selected to lieanywhere within a fairly broad range of values without significantlyaffecting performance. The preferred pressure range is from about 0.1 toabout 2 Torr, although pressures outside of that range can also be used.In addition, the frequencies that were chosen for the describedembodiment were merely illustrative and the frequencies that may be usedin the invention are not restricted to those used in the describedembodiment. For example, with regard to the RF power source, any of awide range of frequencies (e.g., 400 KHz to 13.56 MHz) are typicallyused to generate plasmas and those frequencies may also be used in theinvention. In general, however, it should be understood that the powerlevels, flow rates, and pressure that are chosen are system specific andthus the will need to be optimized for the particular system in whichthe process is being run. Making the appropriate adjustments in processconditions to achieve optimum of performance for a particular system iswell within the capabilities of a person of ordinary skill in the art.

Programming

The system controller operates under the control of a computer programstored on the hard disk drive of a computer. The computer programdictates the process sequencing and timing, mixture of gases, chamberpressures, RF power levels, susceptor positioning, slit valve openingand closing, wafer heating and other parameters of a particular process.The interface between a user and the system controller is preferably viaa CRT monitor and lightpen which is depicted in FIG. 8. In a preferredembodiment two monitors are used, one monitor mounted in the clean roomwall for the operators and the other monitor behind the wall for theservice technicians. Both monitors simultaneously display the sameinformation but only one lightpen is enabled. The lightpen detects lightemitted by the CRT display with a light sensor in the tip of the pen. Toselect a particular screen or function, the operator touches adesignated area of the display screen and pushes the button on the pen.The display screen generally confirms communication between the lightpenand the touched area by changing its appearance, i.e. highlight orcolor, or displaying a new menu or screen.

A variety of processes can be implemented using a computer programproduct that runs on, for example, the system controller. The computerprogram code can be written in any conventional computer readableprogramming language such as for example 68000 assembly language, C,C++, or Pascal. Suitable program code is entered into a single file, ormultiple files, using a conventional text editor, and stored or embodiedin a computer usable medium, such as a memory system of the computer. Ifthe entered code text is in a high level language, the code is compiled,and the resultant compiler code is then linked with an object code ofprecompiled library routines. To execute the linked compiled objectcode, the system user invokes the object code, causing the computersystem to load the code in memory, from which the CPU reads and executesthe code to perform the tasks identified in the program.

FIG. 25 shows an illustrative block diagram of a preferred hierarchicalcontrol structure of the computer program 1410. A user enters a processset number and process chamber number into a process selector subroutine1420 in response to menus or screens displayed on the CRT monitor byusing the lightpen interface. The process sets provide predeterminedsets of process parameters necessary to carry out specified processes,and are identified by predefined set numbers. The process selectorsubroutine 1420 identifies (i) the desired process chamber, and (ii) thedesired set of process parameters needed to operate the process chamberfor performing the desired process. The process parameters forperforming a specific process relate to process conditions such as, forexample, process gas composition and flow rates, temperature, pressure,plasma conditions such as RF bias power levels and magnetic field powerlevels, cooling gas pressure, and chamber wall temperature and areprovided to the user in the form of a recipe. The parameters specifiedby the recipe are entered in any conventional manner, but mostpreferably by utilizing the lightpen/CRT monitor interface.

Electronic signals provided by various instruments and devices formonitoring the process are provided to the computer through the analoginput and digital input boards of the system controller. Anyconventional method of monitoring the process chambers can be used, suchas polling. Furthermore, electronic signals for operating variousprocess controllers or devices are output through the analog output anddigital output boards of the system controller. The quantity, type andinstallation of these monitoring and controlling devices may vary fromone system to the next according to the particular end use of the systemand the degree of process control desired. The specification orselection of particular devices, such as the optimal type ofthermocouple for a particular application, is known by persons withskill in the art.

A process sequencer subroutine 1430 comprises program code for acceptingthe identified process chamber number and set of process parameters fromthe process selector subroutine 1420, and for controlling operation ofthe various process chambers. Multiple users can enter process setnumbers and process chamber numbers, or a user can enter multipleprocess chamber numbers, so the sequencer subroutine 1430 operates toschedule the selected processes in the desired sequence. Preferably, theprocess sequencer subroutine 1430 includes program code to perform thesteps of (i) monitoring the operation of the process chambers todetermine if the chambers are being used, (ii) determining whatprocesses are being carried out in the chambers being used, and (iii)executing the desired process based on availability of a process chamberand type of process to be carried out. When scheduling which process isto be executed, the sequencer subroutine 1430 can be designed to takeinto consideration the present condition of the process chamber beingused in comparison with the desired process conditions for a selectedprocess, or the "age" of each particular user entered request, or anyother relevant factor a system programmer desires to include fordetermining the scheduling priorities.

Once the sequencer subroutine 1430 determines which process chamber andprocess set combination is going to be executed next, the sequencersubroutine 1430 causes execution of the process set by passing theparticular process set parameters to a chamber manager subroutine1440a-c which controls multiple processing tasks in a process chamber106 according to the process set determined by the sequencer subroutine1430. For example, the chamber manager subroutine 1440a comprisesprogram code for controlling sputtering and CVD process operations inthe process chamber 106. The chamber manager subroutine 1440 alsocontrols execution of various chamber component subroutines whichcontrol operation of the chamber component necessary to carry out theselected process set. Examples of chamber component subroutines arewafer positioning subroutine 1450, process gas control subroutine 1460,pressure control subroutine 1470, heater control subroutine 1480, andplasma control subroutine 1490. Those having ordinary skill in the artwill recognize that other chamber control subroutines can be includeddepending on what processes are desired to be performed in the processchamber 106. In operation, the chamber manager subroutine 1440aselectively schedules or calls the process component subroutines inaccordance with the particular process set being executed. The chambermanager subroutine 1440a schedules the process component subroutinessimilarly to how the sequencer subroutine 1430 schedules which processchamber 106 and process set is to be executed next. Typically, thechamber manager subroutine 1440a includes steps of monitoring thevarious chamber components, determining which components need to beoperated based on the process parameters for the process set to beexecuted, and causing execution of a chamber component subroutineresponsive to the monitoring and determining steps.

Operation of particular chamber components subroutines will now bedescribed with reference to FIG. 25. The wafer positioning subroutine1450 comprises program code for controlling chamber components that areused to load the wafer onto the pedestal 628, and optionally to lift thewafer to a desired height in the chamber 106 to control the spacingbetween the wafer and the showerhead 642. When wafers are loaded intothe chamber 106, the pedestal 628 is lowered and the lift pin assemblyis raised to receive the wafer and, thereafter, the pedestal 628 israised to the desired height in the chamber, for example to maintain thewafer at a first distance or spacing from the gas distribution manifoldduring the CVD process. In operation, the wafer positioning subroutine1450 controls movement of the lift assembly and pedestal 628 in responseto process set parameters related to the support height that aretransferred from the chamber manager subroutine 1440a.

The process gas control subroutine 1460 has program code for controllingprocess gas composition and flow rates. The process gas controlsubroutine 1460 controls the open/close position of the safety shut-offvalves, and also ramps up/down the mass flow controllers to obtain adesired gas flow rate. The process gas control subroutine 1460 isinvoked by the chamber manager subroutine 1440a, as are all chambercomponents subroutines, and receives from the chamber manager subroutineprocess parameters related to the desired gas flow rate. Typically, theprocess gas control subroutine 1460 operates by opening a single controlvalve between the gas source and the chamber 106 gas supply lines, andrepeatedly (i) measuring the mass flow rate, (ii) comparing the actualflow rate to the desired flow rate received from the chamber managersubroutine 1440a, and (iii) adjusting the flow rate of the main gassupply line as necessary. Furthermore, the process gas controlsubroutine 1460 includes steps for monitoring the gas flow rate for anunsafe rate, and activating a safety shut-off valve when an unsafecondition is detected.

In some processes, an inert gas such as argon is provided into thechamber 106 to stabilize the pressure in the chamber before reactiveprocess gases are introduced into the chamber. For these processes, theprocess gas control subroutine 1460 is programmed to include steps forflowing the inert gas into the chamber 106 for an amount of timenecessary to stabilize the pressure in the chamber, and then the stepsdescribed above would be carried out. Additionally, when a process gasis to be vaporized from a liquid precursor, for exampletetraethylorthosilane (TEOS), the process control subroutine 1460 wouldbe written to include steps for bubbling a delivery gas such as heliumthrough the liquid precursor in a bubbler assembly. For this type ofprocess, the process gas control subroutine 1460 regulates the flow ofthe delivery gas, the pressure in the bubbler, and the bubblertemperature in order to obtain the desired process gas flow rates. Asdiscussed above, the desired process gas flow rates are transferred tothe process gas control subroutine 1460 as process parameters.Furthermore, the process gas control subroutine 1460 includes steps forobtaining the necessary delivery gas flow rate, bubbler pressure, andbubbler temperature for the desired process gas flow rate by accessing astored data table containing the necessary values for a given processgas flow rate. Once the necessary values are obtained, the delivery gasflow rate, bubbler pressure and bubbler temperature are monitored,compared to the necessary values and adjusted accordingly.

The pressure control subroutine 1470 comprises program code forcontrolling the pressure in the chamber 106 by regulating the size ofthe opening of the throttle valve in the exhaust system of the chamber.The size of the opening of the throttle valve is varied to control thechamber pressure at a desired level in relation to the total process gasflow, the gas-containing volume of the process chamber, and the pumpingset point pressure for the exhaust system. When the pressure controlsubroutine 1470 is invoked, the desired set point pressure level isreceived as a parameter from the chamber manager subroutine 1440a. Thepressure control subroutine 1470 operates to measure the pressure in thechamber 106 using one or more conventional pressure manometers connectedto the chamber, compare the measured value(s) to the set point pressure,obtain PID (proportional, integral, and differential) control parametersfrom a stored pressure table corresponding to the set point pressure,and adjust the throttle valve according to the PIID values obtained fromthe pressure table. Alternatively, the pressure control subroutine 1470can be written to open or close the throttle valve to a particularopening size to regulate the chamber 106 to the desired pressure.

The heater control subroutine 1480 comprises program code forcontrolling the temperature of the lamp or heater module that is used toheat the wafer 502. The heater control subroutine 1480 is also invokedby the chamber manager subroutine 1440a and receives a desired, or setpoint, temperature parameter. The heater control subroutine 1480determines the temperature by measuring voltage output of a thermocouplelocated in a pedestal 628, compares the measured temperature to the setpoint temperature, and increases or decreases current applied to theheater to obtain the set point temperature. The temperature is obtainedfrom the measured voltage by looking up the corresponding temperature ina stored conversion table, or by calculating the temperature using afourth order polynominal. When radiant lamps are used to heat thepedestal 628, the heater control subroutine 1480 gradually controls aramp up/down of current applied to the lamp. The gradual ramp up/downincreases the life and reliability of the lamp. Additionally, abuilt-in-fail-safe mode can be included to detect process safetycompliance, and can shut down operation of the lamp or heater module ifthe process chamber 106 is not properly set up.

The plasma control subroutine 1490 comprises program code for settingthe RF bias voltage power level applied to the process electrodes in thechamber 106, and optionally, to set the level of the magnetic fieldgenerated in the chamber. Similar to the previously described chambercomponent subroutines, the plasma control subroutine 1490 is invoked bythe chamber manager subroutine 1440a.

While the system of the present invention was described above withreference to a plasma enhanced CVD application, it is to be understoodthat the invention also includes the use of high density (HDP) CVD andPVD chambers as well as etch chambers. For example, the system of thepresent invention can be adapted to include tandem HDP CVD chambers forplasma processing. In one alternative embodiment, the gasdistribution/lid assembly could be replaced with a dielectric domehaving an inductive coil disposed about the dome and an RF power supplyconnected to the coil to enable inductive coupling of a high densityplasma within the chamber. Similarly, tandem PVD chambers could beconfigured with a target assembly disposed thereon for a depositionmaterial source. DC power supplies could be connected the targetassemblies to provide sputtering power thereto.

While the foregoing is directed to the preferred embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof. The scope of theinvention is determined by the claims which follow.

What is claimed is:
 1. An apparatus for exciting one or more gasesoutside of a processing chamber, comprising:(a) at least one gas inletselectively connectable to a chamber gas feed; (b) at least one gasoutlet; (c) an energy transparent conduit disposed between the gas inletand the gas outlet; (d) a power source connected to deliverplasma-generating power to the conduit; and (e) a gas distributionassembly connected to the gas outlet for delivering the excited gasesinto the processing chamber, the gas distribution assembly comprising agas passage that terminates in the processing chamber between a blockerplate having a central gas passage and a gas distribution plate having aplurality of gas distribution holes.
 2. The apparatus of claim 1 furthercomprising an enclosure disposed about the conduit.
 3. The apparatus ofclaim 2 wherein the power source is connected to deliver power into theenclosure.
 4. The apparatus of claim 3 wherein the power source isconnected to the enclosure by a waveguide.
 5. The apparatus of claim 1wherein the gas passage terminates at an edge of the gas distributionplate.
 6. The apparatus of claim 1 wherein each gas inlet is connectedto a tee that connects the gas inlet to a second processing chamber andto the chamber gas feed.
 7. The apparatus of claim 1 wherein theapparatus is mounted on a lid of the processing chamber.
 8. Theapparatus of claim 1 wherein the power source is a microwave source. 9.The apparatus of claim 8 wherein the microwave source is a conventionalmicrowave generator.
 10. The apparatus of claim 9 wherein the microwavegenerator delivers about 500 to about 1500 watts to the energytransparent conduit.
 11. The apparatus of claim 10 wherein the pressurewithin the energy transparent conduit is maintained at about 0.5 toabout 2.5 torr.
 12. The apparatus of claim 1 wherein the gasdistribution assembly terminates within a a shower-head assemblydisposed in the processing chamber.
 13. The apparatus of claim 6 whereinthe chamber gas feed is connected to a mixing filter disposed prior tothe tee.
 14. The apparatus of claim 1 further comprising a processingchamber having a side wall portion, a bottom portion and a top portion;the side wall portion defining at least one gas passage having a gaspassage inlet disposed at the bottom portion and a gas passage outletdisposed at the top portion.
 15. The apparatus of claim 14 wherein thetop portion comprises a chamber lid having at least one openingadaptable to receive the gas distribution assembly.
 16. The apparatus ofclaim 15 further comprising at least one gas line connecting the gaspassage outlet at the top portion of the chamber and the gas inlet ofthe apparatus.
 17. The apparatus of claim 14 further comprising achamber plasma generator connected to deliver plasma-generating power tothe chamber.
 18. The apparatus of claim 1 further comprising a filterdisposed between the gas outlet and the gas distribution assembly. 19.The apparatus of claim 18 wherein the filter comprises a porous ceramicmaterial.
 20. The apparatus of claim 19 wherein the porous ceramicmaterial has a pore size between about 0.01 μm and about 0.03 μm. 21.The apparatus of claim 18 wherein the filter comprises Teflon.